What happened
On March 19, 2020, a near-collision occurred at Langenthal airfield (LSPL) during the final approach to runway 23. The first aircraft, a Robin DR 400/180 R (registration HB-KBP), had recently completed a glider tow and was performing a standard approach. Simultaneously, a Votec 322 (registration HB-YLC) was arriving from Grenchen, flying a non-standard approach pattern used by local glider groups for noise abatement.
The pilot of the HB-YLC was performing a power-off slip, which resulted in a higher approach speed of approximately 161 km/h compared to the HB-KBP's 115 km/h. As the HB-KBP initiated its flare roughly 200 meters from the runway, the faster HB-YLC overtook it, passing just above the aircraft. The sudden wake turbulence from the passing Votec 322 forced the pilot of the HB-KBP to apply full power and execute a go-around. At the closest point, the two aircraft were separated by only about 80 meters horizontally and 10 meters vertically.
The investigation
SUST examined the flight paths, cockpit equipment, and communication effectiveness. The investigation established that the pilot of the HB-YLC could not clearly understand radio transmissions because the right earphone of his headset was broken, making engine noise a significant distraction. Furthermore, the HB-KBP was flying with its transponder turned off, and the HB-YLC did not yet have a Powerflarm system installed, meaning neither pilot received electronic collision warnings.
Findings
- The pilot of the HB-YLC incorrectly assumed the HB-KBP would remain on the ground due to seeing other aircraft on the taxiway.
- The pilot of the HB-KBP assumed the higher-flying HB-YLC would continue toward the Jura mountains rather than turning into the final approach.
- The use of non-published approach patterns (right-hand base) increased the risk of undetected traffic.
- Broken communication equipment and the lack of active transponder/collision avoidance signals prevented early detection of the conflict.
Safety action
- The investigation noted that using approach procedures not documented on the Visual Approach Chart (VAC) remains a risk factor.
- It was highlighted that all arrival and departure procedures should be officially published by authorities to ensure all pilots are aware of them, regardless of how frequently they are used.